<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8">   
 <title>开始学习css了</title>
<style>
    #para1
    {
        color: red;
        text-align:center;
    }
    </style>
    </head>
    <body>
        <p id="para1">Hellow world!</p>
        <p>这个段落不受该样式影响。</p>
    </body>
    </html>